Solenoid valve housing matters

Published: August 28, 2024

The housing shields the coil and moving parts of a solenoid valve while serving as the dimensional datum for assembly. Its machining quality directly impacts sealing integrity, magnetic circuit performance, and overall service life.

What is a solenoid valve housing?

A solenoid valve housing is the drawn metal shell that carries the coil, the plunger and the seal of a solenoid valve. It is also called a solenoid housing, a valve body shell, or - on fuel and air-suspension valves - a magnetic sleeve or magnet frame. It is a formed part rather than a casting or a weldment: a blank is deep drawn into a cup, redrawn or ironed to the finished wall, and machined only where it seals or locates, which keeps the magnetic circuit continuous and the part leak-tight with no seam. Housings we quote run from about 0.3 mm to 1.5 mm of wall, and the grade is chosen for the magnetic duty as much as for strength: low-carbon steel and pure iron where flux matters, 304 or 316L where the valve sees coolant or fuel, brass where it is soldered into a manifold.

I. Material selection

Choose stainless steel, low-carbon steel, aluminum, or another alloy based on corrosion resistance, magnetic properties, strength, and the working medium. Keep the grade and incoming material condition traceable through mill certs and lot records.

II. Machining accuracy

Control the inner diameter, outer diameter, concentricity, flange flatness, and assembly features to the print. Coordinate deep drawing and secondary machining up front so accumulated tolerances stay within spec and don't drift across the run.

III. Sealing treatment

Sealing faces must be free of burrs, cracks, and draw marks. Match groove dimensions and surface finish to the chosen seal, and run leak testing where the application calls for it—don't skip it on critical media.

IV. Processing technology

The draw ratio, tooling radii, lubrication, and intermediate annealing determine whether the housing forms without thinning or wrinkling. Also make sure any surface treatment is compatible with the base metal and the final operating environment.

V. Quality inspection

Inspection typically covers appearance, dimensions, material verification, coating thickness, cleanliness, and sealing performance. Set up control plans and gauges before mass production starts, not after issues surface.

In conclusion, reliable solenoid valve housings come from tight coordination across material selection, machining accuracy, sealing, manufacturing process, and inspection—each step feeds the next.

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How a solenoid valve housing is made at Balford

A solenoid valve housing starts as a blank cut from strip and ends as a measured part, and every operation between the two exists to hold one of three things: the magnetic circuit, the bore, or the sealing face. Balford runs this sequence on its own presses from 25 t to 350 t, with a maximum draw diameter of 250 mm; more than 4,000 single-hit drawing dies have been built since 2000.

• Blank and first draw. The blank is cut from strip and drawn into a cup in one stroke. Draw ratio, tool radius and clearance at this step decide how much the wall thins and where.
• Redraw and ironing. A housing deeper than one draw allows is redrawn through further stages; where the wall has to be thinner than the blank, the part is ironed through a series of rings instead of drawn again.
• Trim, pierce and form. The flange is trimmed to length, holes and slots are pierced, and assembly features are formed in the same die where the geometry allows it.
• Magnetic annealing. Where the housing is part of the magnetic circuit, the draws have work-hardened the material and reduced its permeability, so the part is annealed after forming. This step runs at an outside heat-treatment partner under our process sheet, with records returned per lot.
• Machining. The bore, the seat and the sealing faces are machined after forming, because that is where a tight tolerance is actually needed.
• Finishing. Passivation, electropolishing and plating are subcontracted; each lot comes back with process records.

What wall thickness and tolerances can a solenoid valve housing hold?

Solenoid valve housings are drawn with walls that commonly run from about 0.3 mm to 1.5 mm, set by the punch-to-die gap rather than by the incoming strip tolerance; a wall thinner than that is possible, but it has to be reached by ironing rather than by a single draw. Three figures decide whether the housing works: the wall and the height at which it is measured, the bore diameter and its concentricity to the outside diameter, and the flatness of the sealing face. On a drawn wall a general tolerance such as +/-0.05 mm is realistic at a stated height; the tighter callouts belong on the machined bore and seat, which are cut after forming. Dimensions to 0.001 mm are agreed in advance only for selected machined features and have to be confirmed against the drawing - they are not a standard tolerance for a drawn wall.

Which material belongs in which solenoid valve housing?

The grade is chosen for the magnetic duty first and the environment second. Low-carbon steel and pure iron carry the flux best and are the usual choice on the armature side of a fuel or air-suspension valve, where the housing is part of the magnetic circuit. 304 and 316L are used where the valve sees coolant, fuel or condensation and corrosion resistance outweighs permeability. Brass is chosen where the housing is soldered or brazed into a manifold and machinability matters more than flux. The grade also decides how many draw stages are possible before an anneal is needed: stainless steel work-hardens faster than low-carbon steel and tolerates less thinning per stage.

What actually decides whether a solenoid housing is leak-tight?

Leak-tightness is decided before the seal is fitted. A drawn housing has no weld seam, so the paths that remain are the sealing face, the bore-to-seat geometry, and any crack the draw opened up at the bottom radius. Three controls matter. The bottom radius has to be generous enough for the material and the draw ratio, or it cracks. The sealing face is machined after forming so that it is flat and free of draw marks. And the wall has to be thick enough at the thread or the press-fit to take the assembly load without yielding. Burrs from piercing and trimming are removed in the same setup, because a burr under a seal behaves exactly like a scratch across the face.

What to put on a solenoid valve housing drawing

• Wall thickness as a nominal with a tolerance band, plus the height at which it is measured.
• Bore diameter, and concentricity against the outside diameter - state which of the two is the datum.
• Sealing face: flatness, surface finish, and whether it is machined or as-formed.
• Material grade, and the magnetic requirement if the housing is part of the flux path.
• Whether the part is annealed after forming, and which surface treatment applies.
• The assembly load the thread or press-fit has to carry.

What we do not claim about solenoid housings

• We are not IATF 16949 certified. Our controls are aligned with IATF 16949 requirements, and we say so rather than claiming the certificate.
• Our quality system is certified to ISO 9001:2015. ISO 14001:2015 has lapsed and is not claimed.
• Magnetic annealing, bulk heat treatment, plating, passivation and electropolishing are carried out by qualified partners with traceable records; they are not run in our own plant.
• We do not publish a defect rate or a zero-late-delivery claim.

Frequently asked questions about solenoid valve housings

What is the difference between a solenoid housing and a solenoid valve body?

In the parts we quote, the housing is the drawn shell that carries the coil and the moving armature, while the valve body is the part that carries the fluid path and the ports. On many valves the two are separate parts joined by a thread, a press-fit or a braze. When a customer says housing they usually mean the magnetic shell; when they say body they mean the ported part.

Can a drawn solenoid housing be made without a weld seam?

Yes, and that is the reason to draw it rather than weld it. Deep drawing forms the shell from a single blank, so there is no longitudinal weld and no heat-affected zone across the magnetic path. A welded tube would put a seam straight through the flux path and add a leak path at the same time.

Which tolerance matters most on the drawing?

Whichever one the seal or the armature rides on. In practice that is the bore diameter and its concentricity to the outside diameter, plus the flatness of the sealing face. The wall matters for strength and for the magnetic section, but it is the bore and the face that decide whether the valve functions.

Do you anneal the housing after drawing?

Where the housing is part of the magnetic circuit, yes. The draws work-harden the material and reduce permeability, so the part is magnetically annealed after forming. That step runs at an outside heat-treatment partner under our process sheet, and the lot comes back with process records.